Apparatus and method for forming seamless flexible tubing



g- 9, 1955 J. M. JOHNSTON 2,714,919

APPARATUS AND METHOD FOR FORMING SEAMLESS FLEXIBLE TUBING Filed Marcih 20, 1951 INVENTOR Unitct APPARATUS AND METHOD FOR FORMING SEAMLESS FLEXIBLE TUBING John M. Johnston, Hillside, N. J. Application March 20, 1951, Serial No. 216,634 13 Claims. (Cl. 153-73) This invention relates to apparatus and method for the 3 provements in the method of manufacturing helically a convoluted flexible tubing.

It has been proposed heretofore to form helical convolutions in straight-walled tubing of ductile metal by rolling helical grooves in the tubing wall. Various shapes and arrangements of rollers, both internal and external 12" to the tube, have been suggested in attempts to accomplish the desired result. In these prior arrangements the axes of the rollers were parallel, or nearly parallel, to the axis of the metal tubing.

It also has been proposed to form helical convolutions in straight-walled metal tubing by feeding the tubing into a relatively rotating, die-like structure having one or more groove-forming die plates providing a working surface arranged in a spiral helix for forming the helical corrugations in the tubing wall. Various die-like structures have been proposed for this purpose. These dies usually are of involved structural design and in many cases are incapable of accommodating readily or fully for normal slight variations in tube size or wall thickness such as may be encountered in actual operation. As a result, the characteristics of the convoluted tubing were not uniform.

Many of these structures which have been proposed for forming helical convolutions in straight-walled metal tubing are difficult and costly to manufacture. Some of them twist or otherwise distort the tube being operated upon and produce unequal strains therein. Many of these devices are subject to excessive wear, with accompanying variation in the finished product and a high upkeep or replacement cost for the apparatus.

It is an object of this invention to provide improved apparatus and method suitable for forming helical convolutions or grooves in straight-walled tubing of ductile material. A further object of the invention is to provide apparatus of the character described which will produce seamless, flexible, metal tubing of uniform quality which is substantially free from distortion and unequal strains. Another object of the invention is to provide apparatus of the character described in which adjustments, when necessary, may be easily made to produce corrugated tubing of high uniformity regardless of slight variations in the size or thickness of the straight-walled tubing. Other objects and advantages of the invention will appear hereinafter.

A preferred embodiment of the invention has been selected for purposes of illustration and is shown in the accompanying drawings, wherein,

Figure 1 is a side elevation of a tube corrugating machine, in somewhat diagrammatic form, showing a straight-walled metal tube about to enter the machine;

Figure 2 is a transverse section, to enlarged scale, showing the straight-walled tube in the mechanism which holds it against rotation during the corrugating process;

States Patent 0 Figure 3 is a view, also to enlarged scale as compared with Figure 1, showing the corrugation forming mechanism in greater detail;

Figure 4 is a vertical section substantially on line 4-4 of Figure 3; and

Figure 5 is a side view of the corrugated tubing, the left-hand portion of this figure showing the tubing substantially as it comes from the corrugating machine and the right-hand portion showing the tubing substantially as it might appear after it has been compressed.

Referring to the drawings, 11 indicates the base or frame of the machine which is provided with three pedestals 12, 13 and 14 having aligned hearings in their upper ends. The pedestals 13 and 14 are spaced close to each other, whereas the pedestal 12 is at some distance depending on the length of convoluted tubing to be made by the machine. In practice, it may be possible to eliminate the pedestal 13 by suitably designing pedestal 14 and its journal to carry the loads imposed thereon.

Rotatably mounted in the bearing of pedestal 12 is a journal to which is secured a suitable driven member, for example a grooved pulley 15. Also secured to the journal so as to turn therewith is one end of a long arbor 16. This arbor passes loosely through the bear ings in the upper ends of the pedestals 13 and 14, and secured on its other end, beyond the pedestal 14, is the axially aligned worm 17, the function of which will appear hereinafter. The arbor 16 and the worm 17 will rotate with the journal in the pedestal 12 when the journal is driven by rotation of the pulley 15, under the influence of belt 18. The belt 18 will be connected to a suitable driving shaft, not shown.

Rotatably mounted in the bearings of pedestals 13 and 14, loosely enclosing the arbor 16, is a tubular journal 19. Secured to the outside of this journal, preferably between the two pedestals, is a suitable driven member, for example a grooved pulley 20. The pulley 20 is driven by belt 21 connected to a suitable driving shaft, not shown, which may be the same shaft which drives the pulley 15 The pulleys 15 and 20 will be driven in opposite directions. Conveniently they will turn at equal speeds, but the speed of the pulley 20 may be greater than the speed of the pulley 15, if desired. It will be understood that sprocket and chain drives, or gears, or other suitable driving mechanism may be substituted for the belt drives. Desirably, a definite speed relation will be maintained between the two driven journals.

Secured on the end of the journal 19 which projects beyond the pedestal 14, so as to rotate with the journal, is a forming head or die carrier 22. The forming head carries the means which, in co-operatlon with the worm, forms the helical groove in the straight-walled ductile tubing. This forming head preferably is in the form of a chuck, of suitable construction, having mounted thereon a plurality of radially adjustable blocks 23. Rotatably mounted on the blocks 23, in suitable manner, are the groove-forming, gear-like, die wheels 24, to be described. Each of these die wheels is mounted so as to be free to rotate about an axis at right angles, or substantially at right angles, to and displaced to one side of the axis of the worm 17.

In the illustrative embodiment there are two blocks 23 and two gear-like die Wheels 24, diametrically located on the chuck, but it will be understood that a different number of die wheels may be used, depending to some extent on the thickness of the tubing Wall, the ductility of the material from which the tubing is made, and the depth J of groove to be formed. When a plurality of die Wheels are employed, they preferably are spaced uniformly around the chuck and preferably there will be an even number of these die wheels arranged in diametrically opposed pairs.

As may be seen in Figure l, the length of the arbor 16 is made such that the worm 17 which is secured on the end thereof is surrounded through a part of its length by the forming head 22, or at least by the blocks 23 which carry the die wheels 24. The teeth of these die wheels match the thread of the worm loosely, or with what might be termed a considerable amount of backlash. The width of a die wheel tooth plus twice the thickness of the tube wall preferably will be approximately equal to, or only slightly less than, the width of the groove in the worm.

In the manner to be described more fully hereinafter, relative rotation between the forming head and a tubing which is moved longitudinally onto the worm causes these die wheels to force metal of the tubing wall down into the helical groove of the worm and to form a corresponding helical groove in the tubing. It will be apparent that if the teeth of one of the die wheels 24 are in mesh with the thread of the worm 17, either directly or separated merely by the tubing wall, relative rotation between the forming head 22 and the worm 17 will cause the die wheel 24 to be turned about its axis, which axis is at right angles to and displaced to one side of the axis of the worm. The depth of the groove formed in the tubing may be controlled, up to the limiting depths of the worm groove and the gear teeth, by adjusting the blocks 23 radially on the chuck.

Since, in the illustrative embodiment, both the worm and the forming head are rotated, means are provided for holding the tubing 25 against rotation as it is fed onto the worm by being moved along its longitudinal axis, the latter substantially coinciding with the axis of the worm. One suitable device for holding the tubing against rotation is shown in the accompanying drawings, wherein the tubing 25 is passed through non-rotatable apparatus which changes the shape of the tubing from round to roughly polygonal with rounded corners. In

the illustrative embodiment this device comprises simply four flat faced rolls 27 mounted on blocks 28 which, in turn, are mounted on a standard 29 secured to the base 11 in alignment with the three pedestals. The rolls 27 are arranged at 90 from each other around the central opening through the device and the blocks 28 preferably should be radially adjustable on the standard to permit control of the extent to which the tube shape is changed and also to accommodate for tubings of different sizes.

The squaring device 26 is located close to the forming head 22, so that the squared tubing passes directly into the forming head. Desirably the free end of the worm 17 may extend part way between the rolls 27. The outside diameter of the worm 17 preferably is approximately equal to the inside diameter of the round tubing and as the tubing is moved from the squaring device onto r the end of the worm its shape is again brought back to round prior to formation of the helical convolutions therein. However, the tubing will be held against rotation in the forming head by the rolls of the squaring apparatus.

All of the die wheels 24 used in the manufacture of any particular convoluted tubing may be similar. The die wheel 24 generally resembles the worm wheel of a worm and wheel gear, but is provided with a special gear face so that upon relative rotation between the forming head and the tubing the leading edges of the gear teeth will not dig into and tear the straight-walled round tubing. According to this invention the die wheels are made so that the leading edges of the gear teeth, as the forming head rotates about the tubing and the worm, ride over the tubing, and the trailing portions of the gear teeth engage and gradually press material of the tubing down into the groove of the worm.

The die wheel of the present invention is generally fr'u'stro-conic'al in shape, but preferably has a concave circumferential periphery. The radius of the addendum circle at the leading edge of the gear face preferably remains constant or increases gradually at a slow rate for approximately one-half the width of the gear and then increases gradually at a substantially faster rate to its maximum at or near the trailing edge of the gear face. This is shown in Figure 4.

In operation, the blocks 23 of the forming head 22 are adjusted radially so that the teeth of the die wheels 24 will mesh loosely with the groove of the worm 17. This adjustment will be such that as the tubing 25 is moved longitudinally onto the worm, and the metal of the tubing is forced down into the worm groove by the teeth of the die wheels, the thickness of the tubing wall will substantially compensate for the looseness or backlash between the die wheels and the worm. Then the forming head 22 is rotated relatively about the tubing. In the illustrative embodiment this is accomplished by rotating the forming head about the tubing, which is held against rotation by the tube squaring device 26. As the forming head turns, the leading'edges of the teeth of the die wheels 24 ride up over the tubing wall and the trailing portions of the teeth force the metal of the tubing wall down into the groove of the worm, thus forming helical convolutions in the tubing corresponding to those of the Simultaneously with the relative rotation between the forming head and the tubing, the worm 17 is rotated relative to the tubing. By screw action the worm feeds the convoluted tubing continuously along over the worm and onto the arbor 16. In this manner the straightwalled round tubing 25 which is fed longitudinally into the tube squaring device 26 passes between the worm 17 and the die wheels 24 and emerges onto the arbor 16 with helical convolutions corresponding to the thread of the worm.

The length of corrugated tubing which can be made in one piece is limited, so far as the present invention is concerned, only by the length of the arbor 16. When the convoluted tubing "equals or approaches the length of the arbor, the machine will be stopped, the end of the arbor remote from the worm will be released from its journal, and the corrugated tubing removed therefrom. Upon reconnection of the arbor to the journal the machine will be in condition 'to manufacture more convoluted tubing.

Convoluted tubing made by the machine and method of the present invention may show some reduction in overall length as compared with the initial length of the straightwall'ed tube, but the length of the tube wall measured along its sinuous course in a longitudinal section through the convoluted tubing will be found to be substantially greater than the original length of the straight-walled tube.

The apparatus and method of the present invention are particularly suited for the manufacture of seamless, flexible metal tubing of diameters up to about three-quarters of an inch, and for the manufacture of flexible tubing from straight-walled tubes having wall thicknesses up to about 0.01 inch.

The left-hand portion of Figure 5 shows the approximate shape of the convoluted tubing as it passes from the worm onto the arbor. Ordinarily this convoluted tubing will be compressed substantially, as is shown more or less diagrammatically in the right-hand portion of Figure 5, so as to provide greatly increased flexibility. This compression of the tubing may be performed either before or after the convoluted tubing has been removed from the arbor.

The invention herein disclosed may be variously moditied and embodied within the scope of the subjoined claims.

I claim:

1. Apparatus for forming helical convolutions in straight-walled ductile tubing comprising, in combination, a helica'lly grooved worth over which the tubing is to be fed by being moved along its longitudinal axis when that axis substantially coincides with the longitudinal axis of the Worm, the outside diameter of the worm being approximately equal to the inside diameter of the tubing, a forming head surrounding the worm, a die wheel rotatably mounted on said head for forming a helical groove in the tubing by forcing material of the tubing down into the groove of the worm upon relative rotation between the forming head and the tube, said die wheel being mounted to rotate about an axis at right angles to and displaced to one side of the axis of the worm, means to relatively rotating the forming head about the Worm and tubing to form a helical groove in the tubing, and means for simultaneously relatively rotating the tubing and the worm to feed the convoluted tubing thus formed longitudinally along the worm.

2. Apparatus for forming helical convolutions in straight-walled ductile tubing comprising, in combination, a helically grooved worm over which the tubing is to be fed by being moved along its longitudinal axis, a forming head rotatable about the worm, a gear-like d e wheel rotatably mounted on said head for forming a helical groove in the tubing by forcing material of the tubing down into the groove of the worm upon rotation of the forming head about the tubing, said die wheel being mounted to rotate about an axis at right angles to and displaced to one side of the axis of the worm, means for holding the tubing against rotation as it moves along the worm, means for rotating the forming head about the worm and tubing to cause the die wheel to form a helical groove in the tubing, and means for simultaneously rela' tively rotating the tubing and the Worm to feed the convoluted tubing thus formed longitudinally along the worm.

3. Apparatus for forming helical convolutions in straight-walled ductile tubing comprising, in combination, a helically grooved worm over which the tubing is to be fed by being moved along its longitudinal axis, a forming head rotatable about the worm, a gear-lil e die wheel mounted on said head so as to rotate about an axis substantially at right angles to and displaced to one side of the axis of the worm, the said die wheel having teeth matching with the thread of the worm so as to form a helical groove in the tubing as the forming head rotates relatively about the tubing, means for rotating the forming head about the worm and tubing to cause the die wheel to form a helical groove in the tubing, and means for simultaneously relatively rotating the tubing and the Worm to feed the convoluted tubing thus formed longitudinally along the worm.

4. Apparatus for forming helical convolutions in straight-walled ductile tubing comprising, in combination,

a helically grooved worm over which the tubing is to be fed by being moved along its longitudinal axis, a forming head surrounding the worm, a gear-like die wheel rotatably mounted on said head for forming a helical groove in the tubing by forcing material of the tubing down into the groove of the worm upon relative rotation between the forming head and the tubing, said die wheel being mounted to rotate about an axis substantially at right angles to and displaced to one side of the axis of the Worm, means for relatively rotating the forming head about the worm and tubing to cause the teeth of the die Wheel to form a helical groove in the tubing, and means for simultaneously relatively rotating the tubing and the Worm to feed the convoluted tubing thus formed along the Worm.

5. Apparatus for forming helical convolutions in straight-Walled tubing according to claim 4, in which the gear-like die wheel is freely rotatable about its own axis and meshes with the worm, separated only by the tubing Wall, and in which the die wheel rotates about its own axis upon relative rotation of the forming head about the worm.

6. Apparatus for forming helical convolutions in straight-walled tubing according to claim 4, in which there are two gear-like die wheels rotatably mounted at diametrically opposed positions on the head for forming a helical groove in the tubing.

7. Apparatus for forming helical convolutions in straight-Walled tubing according to claim 4, in which there are a plurality of gear-like die wheels rotatably mounted on the head for forming a helical groove in the tubing and in which the die wheels are spaced uniformly about the worm.

8. Apparatus for forming helical convolutions in straight-walled ductile tubing according to claim 4, in which the gear-like die wheel is frustro-conical in shape and has a series of teeth matching the worm thread.

9. Apparatus for forming helical convolutions in straight-walled ductile tubing according to claim 4, in which the gear-like die wheel is frustro-conical in shape and has a concave circumferential periphery formed with a series of teeth matching the worm thread.

10. Apparatus for forming helical convolutions in straight-walled ductile tubing according to claim 4, in which the gear-like die wheel is a worm Wheel which meshes with the worm, and in which the leading edge of the die Wheel, as the forming head rotates about the worm, is formed so that the leading edges of worm wheel teeth ride over the tubing and the trailing portions of the worm wheel teeth engage and gradually press material of the tubing down into the groove of the worm.

11. Apparatus for forming helical convolutions in straight-walled ductile tubing according to claim 4, in which the gear-like die wheel is a Worm wheel having teeth which match the thread of the worm, the radius of the addendum circle at the leading edge of the gea face, as the forming head rotates about the worm, being less than at the trailing edge, so that the leading edges of Worm wheel teeth ride over the tubing and the trailing portions of the worm wheel teeth engage and gradually press material of the tubing down into the groove of the worm.

12. Apparatus for forming helical convolutions in straight-Walled ductile tubing according to claim 11, in which the radius of the addendum circle increases gradually at a slow rate for approximately one-half the width of the face of the gear and then gradually at a substantially faster rate to its maximum.

13. The method of forming helical convolutions in round, straight-Walled, ductile tubing which comprises squaring the tubing, guiding the squared tubing longitudinally from the squaring device directly onto a worm having an outside diameter substantially equal to the inside diameter of the round tubing, forming a helical groove in the tubing by forcing material of the tubing down into the groove of the worm, and rotating the Worm while holding the tubing against rotation in the squaring device so as to feed the convoluted tubing along and over the Worm.

References Cited in the tile of this patent UNITED STATES PATENTS 

